Patent GB-895344-A (GB)
Title: Method of temporary protection of hydroxy, mercapto and amino groups
IPC: C09B43/12
Filed: 1958-08-13
Abstract: The invention comprises an arylazobenzyloxycarbonyl chloride, an organic compound with a hydroxyl, mercapto or amino group acylated by an arylazoarylmethyloxycarbonyl radical and a method for the temporary protection of hydroxyl, mercapto or amino groups by acylation wherein an organic compound containing a hydroxyl, mercapto or amino group is acylated with an arylazoarylmethoxycarbonyl halide. The aryl groups may be phenyl or naphthyl and may be substituted with alkoxy, e.g. methoxy, groups or by halogen atoms.  The arylazobenzyloxycarbonyl chlorides are obtained by reacting the corresponding substituted benzyl alcohols with phosgene in dioxane solution.  The arylazobenzyl alcohols employed as starting materials are obtained by reacting aminobenzyl alcohols with nitrosoaryl compounds, e.g. nitroso benzene or by diazotising aminobenzyl alcohols and coupling with phenol or a -naphthol.  The hydroxy groups may be methylated, e.g. with dimethyl sulphate.  The acylation of the hydroxyl, mercapto and amino groups is preferably carried out in the presence of inorganic or organic bases, e.g. carbonates and hydroxides of alkali- and alkaline earth metals or tertiary amines or pyridine.  The protecting groups may be split off at temperatures below 50 DEG C. in the presence of hydrolyzing or reducing agents, e.g. with dilute hydrobromic acid in glacial acetic acid or by catalytic hydrogenation.  Specific acylated compounds described include p-phenylazobenzyloxy-carbonyl derivatives of glycine, L-alanine, L-valine, L-proline, L-phenylalanine, L-tyrosine, L-tryptophane, L-serine, L-aspargine, L-leucine, L-methionine, L-glutamic acid g -methyl ester and thioglycollic acid, p - (p1 - methoxyphenylazo) - benzyloxycarbonyl derivatives of glycine, L-proline, L-glutamic acid g -methyl ester, L-arginine, L-phenylalanine, testosterone, phenylalanyl-phenylalanine ethyl ester, g -carbomethoxyglutamyl-o-acetyl-tyrosine nitrobenzyl ester (L.L), b -carbomethoxyaspargyl - g  - carbomethoxy - glutamyl - o - acetyl - tyrosine - nitrobenzyl ester (L.L.L), L-lysine, L-valine, L-methionine, L-tryptophane and (im)-benzyl-L-histidine. The preparation is described of p-phenylazobenzyl alcohol, p-methoxyphenylazobenzyl alcohol, m- and p-4-hydroxy and 4-methoxynaphthylazobenzyl alcohols and the corresponding substituted benzyloxycarbonyl chlorides.ALSO:The invention comprises arylazobenzyloxycarbonyl chlorides which are coloured and are employed to protect the hydroxyl, mercapto or amino groups of organic compounds by acylation (see Group IV(b)).  The aryl group may be phenyl or naphthyl and may be substituted with such groups as alkoxy groups or by halogen atoms. The arylazobenzyloxycarbonyl chlorides are obtained by reacting the corresponding substituted benzyl alcohols with phosgene in dioxane solution.  The arylazobenzyl alcohols employed as starting materials are obtained by reacting aminobenzyl alcohols with nitroso aryl compounds, e.g. nitroso benzene or by diazotising aminobenzyl alcohols and coupling, e.g. with phenol or a -naphthol.  The hydroxy groups may be methylated, e.g. with dimethyl sulphate.  The preparation is described of p p-phenyl-azobenzyl alcohol, p-methoxyphenyl-azobenzyl alcohol, m-and p-4-hydroxy- and 4-methoxy-naphthylazobenzyl alcohols and the corresponding substituted benzyloxy-carbonyl chlorides.